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/*
* Copyright (C) 2016 The CyanogenMod Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package cyanogenmod.os;
import android.os.Parcel;
import cyanogenmod.os.Build.CM_VERSION_CODES;
/**
* Simply, Concierge handles your parcels and makes sure they get marshalled and unmarshalled
* correctly when cross IPC boundaries even when there is a version mismatch between the client
* sdk level and the framework implementation.
*
* <p>On incoming parcel (to be unmarshalled):
*
* <pre class="prettyprint">
* ParcelInfo incomingParcelInfo = Concierge.receiveParcel(incomingParcel);
* int parcelableVersion = incomingParcelInfo.getParcelVersion();
*
* // Do unmarshalling steps here iterating over every plausible version
*
* // Complete the process
* incomingParcelInfo.complete();
* </pre>
*
* <p>On outgoing parcel (to be marshalled):
*
* <pre class="prettyprint">
* ParcelInfo outgoingParcelInfo = Concierge.prepareParcel(incomingParcel);
*
* // Do marshalling steps here iterating over every plausible version
*
* // Complete the process
* outgoingParcelInfo.complete();
* </pre>
*/
public final class Concierge {
/** Not instantiable */
private Concierge() {
// Don't instantiate
}
/**
* Since there might be a case where new versions of the cm framework use applications running
* old versions of the protocol (and thus old versions of this class), we need a versioning
* system for the parcels sent between the core framework and its sdk users.
*
* This parcelable version should be the latest version API version listed in
* {@link CM_VERSION_CODES}
* @hide
*/
public static final int PARCELABLE_VERSION = CM_VERSION_CODES.ELDERBERRY;
/**
* Tell the concierge to receive our parcel, so we can get information from it.
*
* MUST CALL {@link ParcelInfo#complete()} AFTER UNMARSHALLING.
*
* @param parcel Incoming parcel to be unmarshalled
* @return {@link ParcelInfo} containing parcel information, specifically the version.
*/
public static ParcelInfo receiveParcel(Parcel parcel) {
return new ParcelInfo(parcel);
}
/**
* Prepare a parcel for the Concierge.
*
* MUST CALL {@link ParcelInfo#complete()} AFTER MARSHALLING.
*
* @param parcel Outgoing parcel to be marshalled
* @return {@link ParcelInfo} containing parcel information, specifically the version.
*/
public static ParcelInfo prepareParcel(Parcel parcel) {
return new ParcelInfo(parcel, PARCELABLE_VERSION);
}
/**
* Parcel header info specific to the Parcel object that is passed in via
* {@link #prepareParcel(Parcel)} or {@link #receiveParcel(Parcel)}. The exposed method
* of {@link #getParcelVersion()} gets the api level of the parcel object.
*/
public final static class ParcelInfo {
private Parcel mParcel;
private int mParcelableVersion;
private int mParcelableSize;
private int mStartPosition;
private int mSizePosition;
private boolean mCreation = false;
ParcelInfo(Parcel parcel) {
mCreation = false;
mParcel = parcel;
mParcelableVersion = parcel.readInt();
mParcelableSize = parcel.readInt();
mStartPosition = parcel.dataPosition();
}
ParcelInfo(Parcel parcel, int parcelableVersion) {
mCreation = true;
mParcel = parcel;
mParcelableVersion = parcelableVersion;
// Write parcelable version, make sure to define explicit changes
// within {@link #PARCELABLE_VERSION);
mParcel.writeInt(mParcelableVersion);
// Inject a placeholder that will store the parcel size from this point on
// (not including the size itself).
mSizePosition = parcel.dataPosition();
mParcel.writeInt(0);
mStartPosition = parcel.dataPosition();
}
/**
* Get the parcel version from the {@link Parcel} received by the Concierge.
* @return {@link #PARCELABLE_VERSION} of the {@link Parcel}
*/
public int getParcelVersion() {
return mParcelableVersion;
}
/**
* Complete the {@link ParcelInfo} for the Concierge.
*/
public void complete() {
if (mCreation) {
// Go back and write size
mParcelableSize = mParcel.dataPosition() - mStartPosition;
mParcel.setDataPosition(mSizePosition);
mParcel.writeInt(mParcelableSize);
mParcel.setDataPosition(mStartPosition + mParcelableSize);
} else {
mParcel.setDataPosition(mStartPosition + mParcelableSize);
}
}
}
}
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